The invention relates to a technology for entrained-flow gasification in which solid and liquid fuels are converted by a gasification medium containing free oxygen under pressures of up to 10 MPa and temperatures of up to 1850° C. into an H2- and CO-rich raw gas. The technology has been described in detail in “Die Veredelung und Umwandlung von Kohle” [The upgrading and conversion of coal], issued by the Deutsche Wissenschaftliche Gesellschaft für Erdöl, Erdgas und Kohle e.V. [German Society for Petroleum, Natural Gas and Coal Science and Technology], section 4.4.3, GSP-Vergasung [GSP gasification].
Accordingly, the raw gas 15, which leaves the reaction chamber at temperatures of up to 1850° C. together with airborne dust and the fuel ash melted into slag, is scrubbed in a quenching chamber by the injection of an excess of water and cooled to water vapor saturation, which at a gasification pressure of for example 4 MPa corresponds to a temperature of about 210° C. The slag collects in the water sump of the quenching chamber and is discharged together with slag water. Together with scrubbing waters and condensates occurring, the excess water from the quenching, as soot water, is subjected to a separation of the solids, to allow it to be recycled to the quenching and scrubbing process.
A dependable measurement of the filling level of the quencher sump 2 in the quenching chamber 1 that is formed by excess quenching water is of particular importance. As FIG. 1 shows, the quenching chamber 1 is arranged downstream of a gasifying chamber (not represented there) by way of a raw-gas and slag inlet 15. The filling-level measurement and control prevents excessive falling or rising of the intended water level. In the first case, raw gas gets into the excess water line 3, in the second case excess water runs into downstream parts of the plant by way of the raw-gas outlet 4. A possible breakthrough of raw gas into the excess water line 3 represents a safety problem, since the downstream soot water installation is not designed for synthesis gas.
To establish the filling level, the pressures in the upper part of the quenching chamber 1 and at the lower end of the quencher sump are measured, the differential pressure recorded by way of a differential-pressure transmitter 6 being a measure of the geodetic height of the water column, and consequently of the filling level 5, and generating the signals for the control for discharging excess water. For measuring the pressure in the quenching chamber 1, it is connected to one side of the differential-pressure transmitter 6. On the other side of the differential-pressure transmitter, there is, by way of a water-filled line 9, the pressure of the quenching chamber 1 together with the pressure resulting from the geodetic height of the quencher sump 2. The sensing of the pressures mentioned is susceptible to problems due to the formation of deposits and accompanying blockages of the measuring lines leading to the transmitter 6, both to the quencher sump 2 and also from the quenching chamber 1, with the result that the measured values are not produced or are falsified, which can lead to the aforementioned operational problems.